Start off by seeing if you're set to show hidden files because they may have that status assigned to them by accident.
Go to My Files or Fle Manager in your Apps list and tap whichever side of the device you need to to find the menu which includes Settings. That should show you a list including Show hidden files. If there's a tick in that, remove it and look through your card again.
Failing that, take the card out of the device and use a carrier to be able to see the files on your PC or laptop. The carriers are quite cheap and look like a full size SdCard but they actually house the micro SdCard your device has so you can connect to another system.